Breast cancer is the second leading cause of cancer death in women, exceeded only by lung cancer, and is the leading cause of earner death among women between the ages of 40 and 55. One out of eight women will develop breast cancer in her lifetime. The American Cancer Society estimates there will be 203,500 new eases of invasive breast cancers diagnosed in 2002. Additionally, in the year 2002, 40,000 deaths in women from breast cancer are anticipated. Early breast cancer screening and detection continues to be a major focus in an effort to lower the mortality rate. Increased use of screening mammography is a major contributing factor to recent improvement in the breast cancer survival rate. In 1999, approximately 30.4 million mammograms were administered. About one million women in the United States are recalled for biopsy annually due to suspect lesions found with mammography, but these suspect lesions am negative in 65% to 80% of the cases. Thus, not only does mammography expose the patient to ionizing radiation, but also to unnecessary biopsies. P-Scan is a recently developed near infrared spectroscopy based optical technology that can detect differences in tissue oxygenation and hemoglobin content. Since many cancers alter local metabolism and produce in the level of blood oxygenation and circulation over an area of surrounding tissue (tumor microcirculatory bed), the P-Scan technology holds promise for being a new metabolism-based noninvasive imaging modality for identifying benign and cancerous suspect lesions identified with mammography. In this application, we propose to develop an ultrasound/P-Scan dual modality imaging system for testing the performance of P-Scan in a small clinical population having suspect lesions with mammography.